When using the zend-mail component
to send email via the ZendMailTransportSendmail transport, a malicious user
may be able to inject arbitrary parameters to the system sendmail program.
The attack is performed by providing additional quote characters within an
address; when unsanitized, they can be interpreted as additional command line
arguments, leading to the vulnerability.

The following example demonstrates injecting additional parameters to the
sendmail binary via the From address:

The attack works because zend-mail filters the email addresses using
the RFC 3696 specification,
where the string "AAA" params injection"@domain is considered a valid
address. This validation is provided using the zend-validator component with
the following parameters:

The above accepts local domain with any string specified by double quotes as the
local part. While this is valid per RFC 3696, due to the fact that sender email
addresses are provided to the sendmail binary via the command line, they create
the vulnerability described above.

Action Taken

To fix the issue, we added a transport-specific email filter for the From
header in the Sendmail transport adapter. The filter checks for the sequence" in the local part of the email From address.